The objectives of this research program are to determine the interrelationship of stimulation of insulin release by glucose and insulin secretogogues with the uptake and efflux of labelled calcium, zinc and cadmium by isolated rat islets. The dual-isotope technique is being used to determine the uptake and efflux of calcium, zinc and cadmium. The intracellular compartmentalization of these substances is being determined on subcellular fractions of islet homogenates. The plasma membrane fraction is being used to determine the kinetics of 45Ca binding to the membranes and to determine the direct effect of glucose on calcium binding. The kinetics of 45Ca binding to other subcellular fractions of the islets will be determined and similar studies will be accomplished with 65Zn. A micromethod for the quantitation of polymerized and depolymerized microtubulin in isolated islets is being established in our laboratory. This assay method will be used to monitor changes in polymerized and depolymerized microtubulin following in vitro culture of the islets for 1-4 days in the presence of low and high concentrations of glucose as well as determining the acute effect of glucose on the state of microtubulin in the islets.